diff --git a/functions/useHttpsCallable.ts b/functions/useHttpsCallable.ts
index ebc0fea..d6ddb5b 100644
--- a/functions/useHttpsCallable.ts
+++ b/functions/useHttpsCallable.ts
@@ -6,7 +6,7 @@ import {
 import { useMemo, useState } from 'react';
 
 export type HttpsCallableHook<RequestData = unknown, ResponseData = unknown> = [
-  (data?: RequestData) => Promise<HttpsCallableResult<ResponseData> | unknown>,
+  (data?: RequestData) => Promise<HttpsCallableResult<ResponseData> | undefined>,
   boolean,
   Error | undefined
 ];